PROPERTY AND EQUIPMENT - Summary of Depreciation and Amortization of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Costs of sales and services	$ 70,368	$ 71,626	$ 70,080
Other depreciation and amortization	2,478	2,274	19,125
Subtotal	72,846	73,900	89,205
Amortization of acquired and developed technologies	2,147	3,048	3,450
Total depreciation and amortization	$ 74,993	$ 76,948	$ 92,655